I don't own a macro lens so take what follows with a pinch of salt please. First of all, don't forget that there are good third party alternatives out there if you need more choices. As for the focal length issue, your zoom lens gets you to 85mm so you can use that to judge pretty well whether a focal length of 100mm will be too long for your intended portrait work. If you think 100mm would be OK then my personal choice would be the EF 100mm f/2.8 Macro USM because of the vignetting of the EF-S 60mm f/2.8 Macro USM lens and, possibly for the future, its incompatibility with full-frame bodies.

Anyway, SLRGear and Photozone have each reviewed both the Canon lenses. The 100mm reviews are here and here and the 60mm reviews are here and here. Both sites also have some reviews on Sigma and Tamron alternatives.

I'm also a non-macro user at the moment so I can't say I'm speaking from experience, but from what I've read either lens performs very well as a 1:1 macro lens.

A few points that I've considered are this:

If you are planning on working with insects and/or little creatures that are skittish then the added working distance of the 100mm may come to your advantage.

But, if you'll be using the lens for double duty such as using it as a portrait lens then I'd stick to the 60mm for a more comfortable working distance. I really enjoy using the 85mm for portrait work, but sometimes feel like it's a little too long (on a cropped body), that's when a 60mm would be perfect.

Ok,
Here's a suggestion,
I get the 100 for macro, which seems to be the more useful one in general.

To satiate my immediate fast portrait lens needs I get the 50mm 1,8 II. This lens is 85€ in Belgium and everywhere I've been reading, it's being praised for its results (for the money that is). I can live with the cheap feeling (it is cheap!) to be able have a f/1.8 when needed.
Is the 1,8 worth of its of 'cheap but does the job very well' reputation?

The 'thrifty-fifty' the 'nifty-fifty', what ever you want to call it, it's a bargain worth owning. It's the lens that will give you the best bang for the buck. It will work as a cheap portrait and low light lens and would compliment your 100mm macro quite well. I see them bought and sold for close to the original price too, so when you're ready to upgrade it to the f/1.4 version you'll get most of your money back out of it. One thing you'll quickly notice is how compact your camera will feel with it on it's a nice size lens for street shooting too.

I really should have reported on them earlier but somehow it flipped, sorry about that.

Yes, I've finally bought the EF-100 and let me just say it, it is an amazing piece of glass. Sharp, accurate and fast. Sometimes I can't believe the amount of detail it manages to capture. I haven't had the time to really properly get into macro but even in a couple of test shots, it was breathtaking.

I've finally choose it over the Ef-S 60 because of several points;

-The increase in working distance really helps, not only in comfort but also by means of light.
-It looked and felt like a more high quality product. It might be just an impression but that's how I've felt.
-The focus-distance limiter really helps, which is not featured in the 60.
-It's not possible in near future (I've just bought me 40D!!) but If ever I want to go full frame, I'd like to carry on using the same kit. (and I have an old EOS 3 film camera as well so Ef-S, I can only buy half hearted.)

The main reason I was interested in the 60 was my aim to also use it as a portrait lens, as the 100 would be a bit long for this but I bought the wonderful ef-50 f/1,8 II for that and frankly, that lens is probably the most fun per € spent.

But if the price difference is a problem and you don't want to have a separate lens around 50mm, I'm sure the 60 will also make you very happy all around.

I hope this helps,
please feel free to ask any more questions you might have.

By the way, if you live around the Benelux countries, Fotokonijnenberg has really unbeatable prices and great, caring staff that know what they are talking about.